Long-term stability evolution mechanism of compressed air energy storage cavern reconstructed in deep anhydrite cavern group

Partial anhydrite rock masses have high strength and large stiffness, and the deep anhydrite cavern group have the potential to be remodeled into compressed air energy storage (CAES) cavern, which has advantages such as short construction period, low cost, and good environmental benefits. During the service period, how the long-term stability of the energy storage cavern evolves is a key engineering problem that restricts the construction of anhydrite CAES. Good long-term stability is a necessary condition for the reconstruction of abandoned anhydrite cavern group into CAES cavern. Revealing the damage evolution mechanism of anhydrite and evaluating long-term stability of the storage under cyclic storage-release conditions are the key problems for the reconstruction of anhydrite CAES. Focusing on the long-term stability evaluation of anhydrite CAES, and based on typical engineering cases, triaxial compression tests of anhydrite under different stress levels were carried out. The damage evolution mechanism of anhydrite rock was revealed, and the fatigue model of anhydrite rock under cyclic loading and unloading was constructed. Considering different storage-release pressures, the damage evolution characteristics of surrounding rock and long-term stability of anhydrite CAES under cyclic storage-release conditions during the service period were evaluated using numerical simulation methods. The results show that with the increase of service life, the surrounding rock damage in anhydrite CAES tends to increase gradually, and the stability of the storage tends to decrease gradually. The cyclic storage-release pressure has a significant effect on the storage long-term stability. To ensure the long-term stability and fully exploit the energy storage potential of the storage, the storage-release pressure of 2–12 MPa is recommended. The research results provide an effective theoretical basis and technical support for the reconstruction of CAES in abandoned anhydrite cavern group.